This invention relates to apparatus for underwater exercise and particularly to means for providing resistance to movement of a user's limbs, e.g. resistance to the movement of a treadmill driven by a user's legs.
The use of exercise apparatus disposed within a body of water, for reducing gravitational stresses on the user's body, are known. While not restricted thereto, the present invention has particular utility in underwater exercise treadmills of the type shown in U.S. Pat. Nos. 4,576,376, 4,712,788, 4,776,581, 3,485,213, and 4,332,217, the subject matter of these patents being incorporated herein by reference. U.S. Pat. Nos. 3,485,213 and 4,332,217 show the use of a treadmill placed in a liquid filled container for exercising animals. U.S. Pat. Nos. 4,576,376, 4,712,788 and 4,776,581 show treadmill and/or cycle type underwater exercise apparatus for use by humans. The above identified patents are of interest, but not one of them discloses a simple mechanism for increasing or varying the resistance to movement of the user's limbs.
This is best explained with reference to the above cited U.S. Pat. No. 4,576,376 to Miller which shows a treadmill which operates a water pump for the purpose of providing resistance to movement of the treadmill belt for increasing the effort of moving the belt (as by walking or jogging thereon) by the user. Means, controllable by the user, are also provided for variably restricting the pump output for selectively varying the resistance to movement of the belt.
A problem with this particular treadmill arrangement is its relative complexity and attendant high cost and weight (the latter being of importance with respect to moving and repairing the apparatus in an underwater environment).
Also, the pump apparatus, and particularly the gearing mechanism described in the patent for driving the pump from the treadmill, is subject to wear and corrosion, particularly within a body of water likely to be chlorinated.
Furthermore, the pump output varying means, for selectively varying the resistance to movement of the belt, while a desirable feature, is somewhat awkward to use, generally requiring a period of trial and error adjustment by the user until the desired resistance is obtained.
Still further, the water pump mechanism is relatively complex, requiring pipes and a valve assembly. Therefore, the resistance controlling mechanism disclosed in U.S. Pat. No. 4,576,376 tends to be complex and expensive.
In sharp contrast thereto, Applicants' invention is directed to a resistance controlling mechanism which is simple and inexpensive to manufacture and which lends itself to be easily adapted for use with many different types of exercise equipment.